Abstract: A method for manufacturing synthetic resin containers which are excellent in strength, toughness and heat insulation and have inner surfaces smooth and agreeable to the touch. The method including the steps of: (a) forming an inner surface layer component from a synthetic resin sheet by thermoforming; (b) fitting the inner surface layer component onto a male die; (c) pouring a synthetic resin in a melt condition into the inside of a female die; (d) fitting the male die onto the female die and bringing it close to the female die to compress the synthetic resin; (e) injecting compressed air into the synthetic resin through at least one air nozzle formed in the female die while enlarging a gap between the male and female dies so as to correspond to a predetermined thickness of a prospective molded product; (f) causing the compressed air to press the synthetic resin against entire inner surface of the cavity; and (g) cooling the synthetic resin to solidify the same and releasing the product from the dies.